Antimicrobial refrigerator air filter

ABSTRACT

An air filter suitable for cleaning the air inside of a refrigerated compartment contains an antimicrobial agent exhibiting biocidal properties against microbes entrained in the air of the compartment. The antimicrobial agent can be associated with the media fibers with a binder.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/580,646, filed on Jun. 17, 2004.

BACKGROUND OF THE INVENTION

The present invention relates generally to an air filter, and morespecifically to an antimicrobial air filter adapted for use in arefrigerated volume.

Refrigerated compartments, and especially the interior of home foodstorage refrigerators, are often subject to substantial changes inhumidity and can contain a high level of moisture. Althoughrefrigeration can slow the growth and proliferation of unwantedmicrobes, microbes can quickly spoil food stored in refrigerators andproliferate on the inner surfaces of the compartment and objectstherein.

Modern refrigeration systems are designed to utilize air flow throughoutthe refrigerated compartment to help achieve a uniform temperaturedistribution within the compartment. Unfortunately, such air flow alsoserves as a medium by which bacteria can be transported throughout theinterior of a refrigerated compartment.

Various devices have been used to filter and clean air inside a space,such as a room, office space, or home. A strong focus of such filteringefforts has been on the removal of allergens from the indoor air of aliving space.

In the air within a refrigerated compartment, various particles andorganisms can be suspended, such as mold spores, bacteria, viruses, andother small particles unable to be trapped in average filters. If nottreated, microorganisms proliferate inside the refrigerated compartment,leading to food spoilage and adverse effects on the taste and aroma ofcertain foods stored therein.

Prior air filtration efforts have used size filters (includingmicrofilters) for contaminant removal, ultraviolet irradiation toneutralize microorganisms, and carbon or charcoal filters to absorbodors.

Filters, including High Efficiency Particulate Air (HEPA) filters, canbe used to cleanse air inside a refrigerated compartment (e.g., aresidential refrigerator, a commercial cooler, a vehicular airconditioning unit, a refrigerated transport vehicle) by “straining”contaminants based on size.

U.S. Pat. Nos. 6,454,841 and 6,736,885 discuss an air filtration systemspecifically designed for refrigerated compartments. The air filtrationsystem consists of a refrigerator and a plenum chamber having an airinlet and an air outlet. The plenum chamber may be inside or outside ofthe refrigerator and is connected to a fan that draws air through theplenum. The plenum chamber holds an air filter assembly that can includea UV radiation source or a polymeric HEPA filter. The '079 documentdiscusses polymeric filter media having a bactericidal agents moldedwithin the polymer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a first embodiment of a refrigeratedcompartment having an air filtration system as disclosed herein.

FIG. 2 is a cross-sectional side view of the air filtration system ofFIG. 1.

DETAILED DESCRIPTION

In one broad aspect, the air filtration system for a refrigeratedcompartment reduces or substantially eliminates microbes, including butnot limited to bacteria, mold, and fungus, from the air within therefrigerated compartment. More specifically, the air filtration systemreduces or substantially eliminates bacteria, mold, fungus, and othermicrobial species from the air inside of a refrigerated compartment suchas a home refrigerator used for food storage.

For ease of discussion, the air filtration system disclosed herein willbe described in the context of a home refrigerator embodiment.

The present air filtration system 10 can bioremediate the air within arefrigerator, reducing the growth and transport of microbes within therefrigerator. This cleaning is accomplished through the use of anantimicrobial air filtration system 10.

The air filtration system 10 according to the present disclosurepreferably comprises a filter assembly 20. The filter assembly 20 has anair inlet port 22 and an air outlet port 24. The filter assembly 20holds a fibrous filter media 30 intermediate the air inlet port 22 andthe air outlet port 24. The fibrous filter media 30 is treated with anantimicrobial agent.

Air drawn through the air inlet port 22 contacts the filter media 30where it comes into intimate contact with the media 30 and associatedantimicrobial agents. The antimicrobial agents work through theirvarious biocidal pathways to eliminate microbes entrained in the air.The air then returns to the interior of the refrigerated compartment Cvia the air outlet port 24.

In a preferred embodiment, the filter is a microfilter. A microfilterhas micropores permeable to air and oxygen and provides the ability tofilter out fine particles such as bacteria and other microorganisms andairborne pollutants. Microfilters can be constructed of a variety ofmaterials which can be of a woven or non-woven material. An example of afilter material is polyester.

Microfilter foils also can be employed for cross flow filtration needs.High Efficiency Particulate Air (HEPA) filters, with a filtration sizerating of approximately 0.3 microns, are also quite effective for theremoval of particulates such as mold spores and pollen.

Referring now to FIG. 1, the fibrous filter media 30 preferably isformed of polymeric fiber. The filter media 30 may be woven or non-woven(the latter shown in FIG. 1). Although the choice of polymeric fiber isnot critical to the function of the filter media 30, polyester is apreferred polymer.

The polymeric fiber may be of any denier suitable for use as filtermedia 30. Generally speaking, however, smaller denier fibers arepreferred as they provide improved filtering capability. In an exemplaryfilter embodiment, the fiber used is polyester fiber, is below 10denier, and more preferably is 6 denier or below.

The embodiment of FIG. 1 comprises two forms of polyester fiber. A firstfiber is 6 denier and represents approximately 60% of the filter media30. A second fiber is 3 denier and represents approximately 40% of thefilter media 30.

In one embodiment, the fibrous filter media 30 is imparted withantimicrobial characteristics by topically treating it with anantimicrobial agent. Unlike methods in which antimicrobial agents areadded to the polymeric melt and distributed throughout the body of thepolymeric article, topical application concentrates the antimicrobialagent on the surface of the individual fibers in the fibrous filtermedia 30. This increased surface concentration improves efficacy againstmicrobes and reduces the overall quantity of antimicrobial agent neededto achieve a particular result.

Many antimicrobial agents are suitable for use with the air filtrationsystem 10, and antimicrobial agents typically utilized with polymerresins are preferred. Particularly preferred antimicrobial agentsinclude chlorinated phenols (e.g., 2,4,4′-trichloro-2′-hydroxydiphenol),silver and silver-containing compounds, azoles, and zinc andzinc-containing compounds (e.g. zinc pyrithione).

In a first preferred embodiment, the antimicrobial agent is added to abinder used to form the polymeric fiber into a non-woven fibrous filtermedia 30. Suitable binders include those used to make non-wovenmaterials. Preferred binders include polymeric resins, with polyesterand latex acrylic resins being preferred polymeric resins. Theantimicrobial agent and the binder should be compatible with each other.

The antimicrobial agent is added to the binder in an amount sufficientto achieve acceptable efficacy when used to form the non-woven fibrousfilter media 30. Of course, achieving acceptable efficacy will also bedependent upon how much binder is utilized and the identity of theantimicrobial agent selected. Those skilled in the art are capable ofdetermining the appropriate amounts of binder and antimicrobial agentwithout undue experimentation.

By way of example, the fibrous filter media 30 shown in FIG. 1 wasformed using polyester fiber of 6 and 3 denier (as discussed above). Anacrylic binder containing approximately 4000 ppm of zinc pyrithione wasused to form the non-woven fibrous filter media 30. The binder wasapplied such that the resulting filter media 30 was approximately 75%(by weight) fiber and 25% resin binder.

Analytical testing indicated the resulting filter media 30 containedabout 1000 ppm zinc pyrithione. Preliminary testing indicated that theresultant filter media 30 was capable of reducing bacterium-sizedairborne particles inside a refrigerator by about 45%.

Turning now to FIG. 2, the fibrous filter media 30 of this embodimentremains disposed within the filter assembly 20 with the aid of varioussupport means which may be provided as part of the air filter assembly20. By way of example, a fitted, or insertable, frame 30 is employed inwhich the filter media 30 may be inserted to slide in and out asdesired. The frame 30 may form an enclosure having an air inlet port 22and an air outlet port 24.

In one alternative arrangement, the frame 30 may only form only one sideof an enclosure by covering an opening the side of the refrigeratedcompartment C. In this instance, the air outlet port 24 would be theopening in the side of the refrigerated compartment C. In a secondalternative arrangement, the filter media 30 may be inserted through aslot or aperture in the housing without perturbation of the air inletand air outlet 22. In either instance the fibrous filter media 30 issituated gaseously intermediate the air inlet port 22 and the air outletport 24.

The air inlet port 22 and the air outlet port 24 (FIG. 2) are in fluidconnection with the interior of the refrigerated compartment C, enablingthe air within the refrigerated compartment C to flow across, flowthrough, and/or come into intimate contact with the fibrous filter media30.

The filter assembly 20 may be held in place by one or more brackets orother suitable mechanical means of attachment. Additionally, adhesive onthe outside portion of the assembly 20 may be utilized.

A plurality of filters may be serially arranged in decreasing pore sizeto extend microfilter life. Larger particulates are thereby trappedwithin the appropriately pore-sized upstream filter, whereas smallerparticulates pass through the upstream filter(s) before becoming trappedby a microfilter having a restrictive pore size.

In such a serial filter arrangement, it would not be necessary toassociate an antimicrobial agent with large-pore filter media throughwhich microorganisms typically could pass. However, large-pore upstreamfilters having antimicrobial properties nonetheless can be employedwithout deviating from the air filtration system 10 disclosed herein.

Means 40 for directing air through the filter assembly 20 is alsoprovided. In one instance, the air directing means 40 is a fan, whichmay be integrated into the filter assembly 20. Alternatively, the filterassembly 20 can be placed adjacent and in fluid communication with anair directing means already present in the refrigerated compartment C.In still another arrangement, the filter media 30 may be combined withthe air directing means 40, for example by shaping a non-woven filtermedia 30 into or combining the filter media 30 with material shaped intoa fan, turbine or other suitable structure used in an air-moving device.

The air filtration system 10 may alternatively be positioned outside ofthe refrigerated compartment C. What is required is the provision of aircontact with, and preferably circulation through, the filter media 30.In most instances, circulation will be accomplished through ducting ortubing, the construction of which is within the skill of one in the art.

One can readily appreciate that air resident within the refrigeratedcompartment may be recirculated therein (as is preferable to maintainthe lowered temperature with reduced energy investment), but also thatfresh, external air could be delivered to the interior of therefrigerated compartment. In this latter case, the filter disclosedherein also can be efficaciously employed to reduce or substantiallyeliminate the introduction of microbes into the interior of thecompartment.

The filtration system 10 is suitable for use in any type of commercialor residential refrigeration unit. For example, the refrigeratedcompartment can also be a retail display case, a commercial transportvehicle, a walk-in cooler/freezer or other industrial installation, andthe like.

It is to be understood that while a certain embodiments of the airfiltration system have been illustrated and discussed herein, it is notto be limited to the specific forms or arrangements presented in thespecification and drawings/figures. It can be appreciated by thoseskilled in the art that various changes may be made without departingfrom the essential features disclosed herein and in the followingclaims.

1. A refrigerated compartment having an air filtration system,comprising: a plurality of walls defining the refrigerated compartment;a filter assembly, the filter assembly having an air inlet port and anair outlet port, the air inlet port and air outlet port being in fluidcommunication with the refrigerated compartment; and a fibrous filtermedia situated between the air inlet port and the air outlet port, atleast a portion of the fibrous filter media being coated with a binder,the binder comprising an antimicrobial agent.
 2. The refrigeratedcompartment of claim 1 wherein the fibrous filter media comprises apolymer.
 3. The refrigerated compartment of claim 2 wherein the polymercomprises polyester.
 4. The refrigerated compartment of claim 1 whereinthe binder comprises an acrylic binder.
 5. The refrigerated compartmentof claim 1 wherein the antimicrobial agent comprises an agent selectedfrom the group consisting of chlorinated phenols, azoles, metals, andzinc pyrithione.
 6. The refrigerated compartment of claim 5 wherein theantimicrobial agent is zinc pyrithione.
 7. The refrigerated compartmentof claim 1, further comprising: means for directing air through thefilter assembly.
 8. A cooling unit air filtration system, comprising: afilter housing having an inlet and an outlet, at least one of the inletand outlet gaseously communicating with a volume to be cooled by thecooling unit; a fibrous filter media disposed between the inlet and theoutlet; a binder coating disposed on at least a portion of the fibrousfilter media; and an antimicrobial agent in association with the binder.9. The system of claim 8 wherein at least one of the inlet or the outletcommunicates with a volume to be cooled by the cooling unit.
 10. Thesystem of claim 8 wherein the fibrous filter media comprises a polymerfiber.
 11. The system of claim 10 wherein the polymer fiber has afineness of 10 denier or less.
 12. The system of claim 10 wherein thepolymer fiber has a fineness of 6 denier or less. 14*. (canceled) 14.The system of claim 10 wherein the polymer comprises polyester.
 15. Thesystem of claim 8 wherein the binder comprises a latex acrylic binder.16. The system of claim 8 wherein the antimicrobial agent comprises anagent selected from the group consisting of chlorinated phenols, silverand silver-containing compounds, azoles, and zinc and zinc-containingcompounds.
 17. The system of claim 16 wherein the antimicrobial agentcomprises zinc pyrithione.
 18. The system of claim 16 wherein theantimicrobial agent comprises 2,4,4′-trichloro-2′-hydroxydiphenol. 19.The system of claim 16 wherein the antimicrobial agent comprises silver.20. The system of claim 8 further comprising: an air flow elementadapted to flow air into gaseous contact with the fibrous filter media.21. The system of claim 10 wherein the fibrous filter media comprises afirst polymer fiber having a first fineness grade and a second polymerfiber having a second fineness grade.